[General Questions and Answers] pe1dnn:
Sorry but the following was contained in my question:

Title: tf300t bootloader save and restore

First line: Is there a way to save and restore the bootloader of an ASUS TF300T tablet?

Deduction:

it is an ASUS

it is a TF300T

it is a tablet

The only thing I didn't mention it is the WW SKU and the latest JB 4.2 bootloader but both are irrelevant. Furthermore:

Last line: The tablet is obviously unlocked already and I have TWRP recovery installed (and am running the fantastic CROMi 5.04 ROM).

Deduction:

its bootloader is unlocked (and it is obvious because with a locked bootloader considering nvflash access is silly and also I installed TWRP which would not have been possible if the bootloader was still locked)

it is has Team Win Recovery Partition installed

it is has a custom ROM CROMi version 5.04 (which should be known by those this in depth knowledge of the TF300T since XDA is its main site and it is currently one of the best ROMs arround for this device)

Further more the body of the message clearly described what I intended to do to give the reader of the question the proper context. So I cannot fathom what other information you expected me to give, it is al there.

I was hoping for somebody to point me to an comprehensive verified instruction since I could not find one and like I said, messing with the bootloader is risky. I asked here instead of a dedicated forum because I just registered and although I'm not a novice the forum rules prohibit posting in the more suitable groups.

For those who like to know, I think I have the blob with the bootloader now. For your information the procedure I used:

Extract "blob" from the ASUS upgrade package (If you download it from the ASUS support site, it is a ZIP. Inside is the update ZIP. Inside the update ZIP there is meta data, update script and the blob)

Get the BlobTool (I just pulled it from Github using "git clone https://github.com/AndroidRoot/BlobTools" and compiled it by typing "make" in the source directory on my Ubuntu 13.04 Linux machine)

Then run the just build blobunpack on the blob from the ASUS upgrade package. This gives several blobs among which blob.EBT

If I understood everything correctly this blob.EBT contains the original unmodified ASUS bootloader. Now I only have to find the guts to try it because with no confirmation of somebody with experience it is still a guess. The blob is not an image and I wonder if TWRP can restore bootloader blobs or that the raw image still has to be extracted from the blob too.

Anyway, an attempt to restore the original bootloader will be after getting nvflash access so even if I brick it the tablet it should be recoverable using the unbrick images. But is is all new and therefore risky and the tablet is currently working fine. So I'm still contemplating if the risk is worth it. It's a shame the stock ASUS JB and later bootloaders do not allow nvflash anymore.

I hope somebody finds this useful, I cannot make any guarantee this is correct. That's why I sought my answer here among the experienced users in the first place.

Your answer did not answer my question but I hope my answer answered yours.