We just did this cable on my buddies MCSS last week.
Couple things we did:
1 - Using a heat gun we bent the locking tabs on the end that clicks into the rectangular boss on the heater box so it locked into place tightly. Otherwise it moves around and could pop out.
2 - We couldn't find the perfect sized retainer clip that holds the cable clip to the pivot bellcrank, so rather then potentially break the little pin trying to force/squeeze/press it on, or next time trying to get it off; we took screw driver tip and heated with torch then flattened it like a little mushroom.
Some might cringe at #2 but to be honest, that bellcrank is available if ever needed, plus just popping off the heater control rod from threads and the cable from retaining clip it can be then be rotated and removed so there's slack to pull the control head side out from dash if needed.
The best advice is just to be careful and don't force anything in the process, plastic is plastic so you're right to want to not break it.
The other end at control head should have screwed on retainer so it should be pretty sturdy.
HTH