Just another community member here, but the hidden columns typically support other functionality in the foundational sheets/tabs and other community solutions. For Accounts, it looks like these columns pull useful data from the Balance History tab and, if you are not using the latest foundation template, you’ll also have Sheet References that feed other formulas. So, I typically leave those ranges alone and do not add content to the right of hidden ranges. However, you can add your columns in range A:E, as I did by adding Owner, without causing problems.
see fine print for possible side effects
It will change the column number/address of the hidden columns. Most formulas dynamically update to accommodate that. Unfortunately, sometimes people hardcode the column address in their formulas rather than using a dynamic lookup for column names, so then you have to troubleshoot it and manually change the column reference in their formula.