Your comments

I think I will keep this after I have done the more generic copy/paste of GA & GTM configs ;)

I thought about that. The good thing is it won't save the variable automatically - so you can always make additional edits or cancel the change.

In that specific case, what you could do is simply copy the current table values, bring them into a Google Sheet where you can reorder, change and add new ones. Then copy those values from the Sheet back into the table. Plus, otherwise, if the current values are left there, you could end up with twice the same rule... which would be even worse.

I thought about have a button to do the copy, and then a paste, and ask specifically if values should be overwritten... but this would be far less intuitive and not as well aligned with the next big feature.

I will make it possible to copy to clipboard the current values from a regex or normal table, and paste from the clipboard - as long as there are two columns: input/pattern and output.

The clipboard data format will have to be separated by a coma, semicolon, a tab, etc. As when you paste to Excel/Google Sheet, use quotes to make sure there's no confusion with the separator.

This could actually be solved if I make it possible to copy the current values from the regex or normal table, and paste them back into a regex or normal table lookup. Refer to the request "Upload data from Google Sheets to regex/lookup tables".

I can't easily alter the functionality of the current widgets.

However, in the specific case you describe, use a time series chart, under Style, change it to column, and enable the comparison period. Voilà! (unless I have misunderstood your request!)

Well... sadly... after looking into it more carefully, there's no easy way to do it because the field element shown on the page doesn't have any indication if it's a custom field or not. I will park this for now but keep it as a potential feature in the future, once I have worked a little bit more on the more advanced modules which will bring subscribers value.