streamlit doesn't support nested columns :(

app.py

@@ -43,7 +43,7 @@ def search_click_callback(search_query, max_results, XRxiv_servers=[]):
     return pdf_info
 
 with st.form(key='columns_in_form', clear_on_submit = False):
-    c1, c2, c3 = st.columns([5, 0.8, 4])
+    c1, c2 = st.columns([5, 0.8])
     with c1:
         search_query = st.text_input("Input search query here:", placeholder='Keywords for most relevant search...', value=''
                                        )#search_query, max_results_current))
@@ -51,17 +51,16 @@ with st.form(key='columns_in_form', clear_on_submit = False):
     with c2:
         max_results = st.number_input("Max papers", value=max_results_current)
         max_results_current = max_results_current
-    with c3:
-        st.markdown('Pre-print server')
-        checks = st.columns(4)
-        with checks[0]:
-            ArXiv_check = st.checkbox('ArXiv')
-        with checks[1]:
-            ChemArXiv_check = st.checkbox('ChemArXiv')
-        with checks[2]:
-            BioArXiv_check = st.checkbox('BioArXiv')
-        with checks[3]:
-            MedrXiv_check = st.checkbox('MedrXiv')
+    st.markdown('Pre-print server')
+    checks = st.columns(4)
+    with checks[0]:
+        ArXiv_check = st.checkbox('ArXiv')
+    with checks[1]:
+        ChemArXiv_check = st.checkbox('ChemArXiv')
+    with checks[2]:
+        BioArXiv_check = st.checkbox('BioArXiv')
+    with checks[3]:
+        MedrXiv_check = st.checkbox('MedrXiv')  
 
     searchButton = st.form_submit_button(label = 'Search')