CONCAT/TEXTJOIN on Variable Number of Cells

Hello!

I have a spreadsheet that looks something like this:
Capture.JPG

I've been trying to come up with a formula that I could paste down column B that will give me this:
Capture2.JPG

There's obviously many ways to do this when you've got 3 groups and 3-5 rows per group but I've got 200 groups (non-empty cells in column A) and they can have anywhere from 2 to 100 values in column C.

I've tried to come up with a TEXTJOIN like TEXTJOIN(",",TRUE,C2:INDIRECT("C"&(2+COUNTBLANK(B2:B###)),TRUE).

I think my problem is that I can't figure out how to count the number of empty cells between two non-empty cells without identifying which cells aren't empty by hand.

Thanks for any help you can provide.

Ya, a macro could definitely handle it. Trying to avoid it if I can.

Was trying to think about a helper column. I was thinking of a MATCH() that gives a list of rows for where the formulas should start and stop. I can't get myself past that, though.

Another way, in B1

=IF(A1="","",SUBSTITUTE(SUBSTITUTE(LEFT(TEXTJOIN(",",1,C1:C100),LEN(TEXTJOIN(",",1,C1:C100))-LEN(TEXTJOIN(",",1,B2:B101)))&",,",",,,",""),",,",""))

The number of rows in each of the 3 ranges would need to be, at minimum equal to the number of rows in the largest group. Note that the last range (column B) starts and ends 1 row below the other ranges. The start cell of this range should be directly below the cell that the formula is entered into.

Just had another quick look at this to see if I could make my suggestion more efficient and came up with the following.

Using a helper column, enter this into D1 and fill down

=IF(OR(A1<>"",C2=""),ROW(D1),"")

Then in B1 and fill down

=IF(A1="","",TEXTJOIN(",",1,C1:INDEX(C:C,SMALL(D:D,COUNT(D$1:D1)+1)-1)))

Noting XOR LX's questions above, both my original single column suggestion from post #6 and this one will work with any combination of those scenarios, Bo_Ry's suggestion from post #5 doesn't appear to work with consecutive non blanks.