Hey @McMonty
The following solution works albeit it it way more complex than I'd like!

1. Create an array of chars which need to be removed from the string: createArray('[',']','"')

2. Add a variable to store the 'Initial value' I've manually set the value...

3. Add a new variable to store the changing / new value

4. Add an 'Apply to each loop'
5. Set the 'Output from previous steps' to the array variable created in step #1
6. Add a 'Set Variable action', add the following expression: replace(variables('InitialValue'),item(),'')

7. Add a 'Set Variable action' to copy the NewValue to the InitialValue variable... you can't self reference in the replace expression 😞
8. Finally... Add a another 'Set Variable' action underneath the 'Apply to each' loop to perform the final replace expression: replace(variables('InitialValue'),',','; ')

Your Flow config should look like this... a little convoluted but it works!:

HTH
Jay
-------------------------------------------------------------------------
If I have answered your question, please mark your post as Solved.
If you like my response, please give it a Thumbs Up.