QGIS print layout: Pulling the name of the map theme from table

Question

Currently I have a table of layout names, that are now linked to some layout template to pull the supplement nr, titel of the map and the sourc(for example AGIV, DOV, etc.)

This I have done by just adding some attribute table frames with the filter "Layout" = @layout_name. Now I want to take this one step further, in the actual table I also have the name of the viewport/theme of the map, normally this was used to keep a record of the theme of the map I should use.

So how do I build the expression that the name of the map theme gets pulled from a certain table (in this case the "QGIS Bijlagen Lijst) or rather from a certain layer without geometry?

Edit: here is the list of name and layer theme, note I have added a fifth variable called scale (schaal). Which is surprise surprise supposed to be the scale of the layout. The formula for the theme should theoretically being used for the scale as well.

Answer 1

The following expression should give you the scale to you layout name.

aggregate('table layer', 'max', CASE WHEN @layout_name like "Lay-out" THEN "Schaal" END)

table layer needs to be replaced with the exact map layer name from the field calculator. You may use this expression as data defined override for your map element.