I kept the list short because I didn't want to have a long comment, but if you want my full list, I'll attach the things I don't think are trivial.

To show you I'm at least somewhat speaking from at least some limited experience, I'll also mark features with a check (/) where I or people next to me at a workplace have maintained or implemented these features and found that they weren't trivial to do. For a few, I've also included one sentence descriptions of why they're not a 1-day project.

My point with this is not to imply that any of this is impossible, just that it isn't free. The question you always need to ask when looking at features on this list is, "how many of these are more important than the core functionality that the client actually cares about?"

And it's not that developers don't care this stuff. I would happily rework our entire app at my current company to have one unified UX everywhere and to add emoji support and play with margins and padding and add a custom dark mode. It would be an enormously fun project. None of our customers would care about it.

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- Change color of things

- Import/export color themes

- Automatic contrast of text if I pick a dark/light background

- Automatically generate color for large number of items

- Use the fonts I use in Office (/) (Most of these fonts are proprietary, and you can't trust the system to expose them. This problem gets a lot more "fun" when you're dealing with multiple languages)

- WYSIWYG editor that behaves like Word (Again, Slack -- it wasn't just that their editor was unwanted, it was buggy and it didn't work, because WYSIWYG editors are hard)

- Emoji support

- Dark theme (how long did Apple take to add this again?)

- My Theme

- Company Branding

- Integrate with system accounts (/)

- Use accounts/permissions from Active Directory (/) (this one isn't too bad, it just takes time, and setting up a testing environment is a huge pain in the neck. It also needs to be optional, because not all of your clients use Active Directory)

- Import from Excel/CSV (/) (Handling misshapen input is hard, clients are extremely creative with how they will break your importer)

- Import from email/email attachment

- Export to PDF/Image (/) (Text complicates things, there is no single right resolution to use)

- Record a short video (/) (Clients want time limits, not space limits, but time limits are unreliable because different mobile devices all record in different resolutions. Clients start using custom recording software that outputs in formats you didn't expect. You discover that browsers are actually very picky about the video formats they'll play, and the only way around that is to transcode videos on the server. This turns out to be wildly expensive.)

- Send as email (/) (BCC rules and sending limits are different for different infrastructures)

- Send as PDF attachment on an email (/) (compression becomes extremely important because of the above)

- Import/attach images (/)

- Use image as background but stretch the right way (based on what?)

- Customizable keyboard shortcuts (/) (not all input devices give the same input codes for the same keys)

- Undo everywhere

- Multiple undo (I'd like to see how the "delay" trick works with this)

- Copy and paste (/) (arbitrary data types in tables make this hard, your table cells have to handle conversions from every data type, including dumb conversions like "I pasted an emoji into a date field". It becomes impossible to deprecate old data types because they need to be updated to handle conversions from new data types)

- Templates (/) (this is just a big thing to build, there's nothing particularly complicated about it. It's like saying, "image editing". Yeah, that's a feature.)

- Video guides that stay up to date

- Screenshots that adapt to my custom setup (how would this work?)

- Translated to my language (/) (you need translators, also hope you're not dynamically concatenating any strings inside of your application, because different languages have different grammar. The proper way to do this is to never write a string and to always call into a parameterized function to get your strings. And in general, writing messages that are easy to translate requires some degree of training.)

- Sorting everywhere (/) (lazy-loaded lists hate this)

- Filtering everywhere (/) (lazy-loaded lists hate this)

- Cascade deletion (/) (see the formulas problem I mentioned before)

- Preview things (/) (see the expensive data operations I mentioned before)

- Progress bars for slow/async operations (/) (Very rarely do you know how long an expensive operation will take. You usually end up guessing)

- Deploy on exotic configurations/platforms (they're called exotic for a reason)

- Deploy on old/unsupported versions (what does this even mean?)

- Deploy on what we have (/) (I already talked about this above)

- Deploy/Run without internet connection (/) (This makes deploy processes about 10 times longer, and makes patching very difficult, because you can't install for the client. You have to trust them to get everything right, and they won't)

- Handle Excel, CSV, JSON, XML (/) (mentioned above)

- Handle malformed versions of all of the above (/) (mentioned above)

- Integrate with obscure/outdated software/format (/) (mentioned above)

- It should work on my old android phone browser/IE 11 (/) (Babel is not a one-click solution to this problem. We support IE 11 of course, but it does eat up a lot of testing time.)

- Works with the database and version we use (/) (mentioned above)