It Will re-appear with raw HTML code if you add a new value on the fly, but it works other than that.
When creating the text formula displayed in the dropdown for the join, use the HTML code for the space or special character you need. For Example, I used the code for a no breaking space, which is when I needed to insert a space, and this works much better on most occasions.
This has been on our roadmap under the name of “Multi Value Dropdowns” for quite some time. We should have this in production within a few days I hope.