OK, relatively simple, but frustrating for me. I think my issue isn't with the TEXTJOIN, but in defining a non-continuous series of cells for the UNIQUE function.
In cell A1, I am using this formula: =TEXTJOIN(" ",UNIQUE(B1,E1,H1,K1,N1))
NOTE: I am trying to do this for a row, and not the entire column that the data is in.
My thought was that it would join only unique values from that series, separated by a hard return.
However, I get an error. Image of a Google Sheet error with my formula
So, looking for a way to look at a non-continuous series of cells in a row, pull out only unique values, and TEXTJOIN them together with a hard return (new line).
Your formula should be
=textjoin(" ",true,unique({B1;E1;H1;K1;N1}))
encapsulate the cells by {}