So, let me get this straight first.
You have a Library table and Journal table. Library table seems to be prefilled with data, but I’m going to guess that data isn’t added or deleted from there (for the most part). Journal is unpopulated and where you plan on adding entries. Both have the same column structure.
In Journal, you have a form where you fill in [Type], [Intensity], [Demand], and [Session]. Now for the part I’m less straight on.
For [WarmUp], [Mainset], and [Cooldown], do you want these to only be visible once the first are filled in? Or do you just want these to auto-populate? Or both?
LOOKUP([ColumnName], "Library", [MatchColumnInLibrary], [ColumnFromLibraryYouWant]
[ColumnName] should be either
[MatchColumnInLibrary] should be the same column. (since you said their identical)
[ColumnFromLibraryYouWant] should be either
[Cooldown] depending on which column this whole expression going in.
If you want them to stay invisible until a value has been computed for these columns, for Show_If:
ISNOTBLANK([_THIS]) should work. Optionally, you can use
CONTEXT("ViewType")<>"Form" to only hide the fields in the Form view.
I’m not sure what your values are supposed to be so, this is about as much help as I can provide at the moment.
And if you need to figure out those last three columns based on the combined entries of the first four, then we may need to switch to a
SELECT(...) expression instead.