Search Value on Multiple Columns and return all associated

Create a new calculated table in Power BI that combines all the salesperson names into a single column. You can use the UNION function to achieve this:

AllSalespersons = UNION(VALUES(Sales[Salesperson 1]), VALUES(Sales[Salesperson 2]), VALUES(Sales[Salesperson 3]))

 Create a DAX measure to calculate the selected salesperson based on the slicer selection. Let's call this measure "SelectedSalesperson":

SelectedSalesperson = SELECTEDVALUE(AllSalespersons, "")

Create another calculated table to filter out the selected salesperson from the "AllSalespersons" table:

OtherSalespersons = FILTER(AllSalespersons, [AllSalespersons] <> [SelectedSalesperson])

Finally, use a table visual and display the "OtherSalespersons" calculated table. This table will show the list of names who worked with the selected salesperson but exclude the selected salesperson itself.
When you use the slicer to select a salesperson, the table visual will dynamically update to display the names of other salespersons who worked with the selected person, excluding the selected person.

Remember to set up the slicer to use the "SelectedSalesperson" measure for its value selection. This way, the slicer controls the filtering based on the selected salesperson.