Combine value from two rows per column: CONCAT or SPLIT/JOIN?

Question

I've tried multiple variations of this formula only to get the same result.

=TRANSPOSE({FILTER('tasks-Groups'!B1:1,'tasks-Groups'!B1:1<>"");FILTER('tasks-Groups'!B2:2,'tasks-Groups'!B1:1<>"")})

=TRANSPOSE({'tasks-Groups'!B1:1;'tasks-Groups'!B2:2})

={TRANSPOSE('tasks-Groups'!B1:1),TRANSPOSE('tasks-Groups'!B2:2)}

But these formulas all print to two columns. What I'd ultimately like to achieve is, in a single column:

B1:B2

C1:C2

D1:D2...

I thought I just needed to concatenate the two ranges, but now I'm beginning to think I need to use SPLIT/JOIN, but not familiar with those functions at all.

Here's my sheet (Sheet49!A2)

Answer 1

to join two columns do this:

=ARRAYFORMULA(A1:A&":"&B1:B)