Today I when I tried to add a change counter, the desired column was not visible among the column choices. I thought this was particularly odd because columns that I could NOT choose because they were of the wrong time (e.g. self-reference to this change column, other change columns, etc.) were visible.
I thought I needed to Regenerate the table to get the platform to “see” the missing column but that did nothing. I was only able to get things to work after “breaking” my app by changing the name of the target column in my Google spreadsheet and adding another column with the same name. To be honest, I can’t remember the exact sequence of steps that worked but, in essence, I feel like I had to change various things until I wound up forcing to take another look at the columns I actually had in my Google sheet (as opposed to what the platform thought I had there).
Though I have no idea about the actual code used in Regenerate on AppSheet platform, I suspect that something about the algorithm that was intended to make it work faster has led it to a less than 100% thorough rebuilding (regeneration) of the table data. My issue has been resolved but I hope the good people at AppSheet can take a look at this.