Hey @10257retoolcom!
In the legacy table, the add row modal takes its settings from the column settings. You can dynamically set the possible values for a tag column by clicking the FX button next to Data source. There you can reference currentRow to change the options based on other values in the row.
This can impact performance though which is part of why it's not possible in the new table, as mentioned in this thread. If you want to have some custom logic when adding new rows you might consider creating an independent modal for your add row form.
Let me know if that helps!