Issue was able to be reproduced on various environments. Whole document set content type and its columns were being installed via pipeline with PnP template.
It turned out, that on every environment, 2nd installation of PnP template fixed the issue. Why is that - any answers will be appreciated.
You can create list columns in SharePoint online using PnP PowerShell.
It's hard to get the ready made script for all types of columns. However, if you understand the cmdlet, it is not difficult to create large number of columns in loop.
Create And Remove List And Fields In SharePoint Site Using PnP Powershell
The txtcontent is "static" and we cannot change the value in txtcontent afte button is cliciking. That is beyond the scope of JSON formatting.
As a workaround, you could update some column value in the flow. And the txtcontent refers to this column. So after clicking the button> trigger the flow > update the column value > the txtcontent ...
How'd you go with this behavior, of PDF's not displaying their sensitivity labels.
I've arrived at very much the same findings as you.
I've researched to see if there are some sort of indexing or timer job that runs and picks these up but nothing has come up.
What did you learn.
For any one else experiencing this issue, I found a solution. It turns out the document library was the thing remembering the internal name of the column. When I deleted the column, remade it, and uploaded a document to a NEW document lib using the column, which had NOT previously used the deleted column, then the internal name of the api response was ...