I want to concatenate a series of columns with each value separated by an underscore in a table

The problem is that the columns to be concatenated are leveraging data validation lists, and not all columns will be used each time the table is updated. How can I concatenate the columns but ensure there are not multiple underscores in a row?

Current output

I’ve tried using the below formula, but this creates a series of multiple underscores.

=B3&"_"&C3&"_"&D3&"_"&E3&"_"&F3&"_"&G3&"_"

Then I tried to use another column to at least remove the trailing underscores which works, but only if I know that there will always be specific number of underscores.

=IF(RIGHT(H5,1)=”_”,LEFT(H5,LEN(H5)-1),H5)

2nd formula

How can I combine inputs within columns B-H, separated by a underscore, but remove an underscore if a drop down is not used?