In SAS EG is there a way to put on hold the execution of a branch (the task would be grayed out for example) so that it's not executed when I execute a parent process ?
If not would you advise a good practice to put some tasks aside without losing the process tree structure ?
You can add a condition as shown in the other answer, and have it depend on a prompt value (if you sometimes might want to run this), or on a macro value that you just define in your program by hand (if you currently never would want to run it).
You won't be able to keep your links, though, without some gymnastics that don't really make sense. Using the conditional execution means not going down the rest of the branch.
I'd also suggest that if you have extra programs that you want to keep-but-not-run, you move them to another process flow, unless you have a very good reason for keeping them in that particular process flow. I usually have a few process flows:
Finally, if you use version control, you can always get back to the program you had before; so if you do use version control properly you don't need to keep programs around just in case, if you're fairly sure they're not needed anymore.