Debugging TSQL in SSMS
The way I am using might not the best, however, just to reassure you that this is possible and it has been working fine for me:

if you really like the debug least for now I am using both versions of ssms, the 17.9 and the 18 side by side as you can see on the picture below:



I use sql server from 2008 r2 up to sql server 2017.