How to make leveling stats (health, magicka, stamina etc.) of an Actor?
I have checked "PC Level Mult", but still stats are as same as at level 1 (I have level 4).
What to do? Is it next bug (how many more?) of Creation Kit or game?

Leveled Summons work well for me.
Is the actor you are trying to level a follower? Have you checked Actor.Getlevel() to see if he does not level at all or if its just his stats that do not change?

I'm making follower which can be summoned (from my storage interiori) using spell. Actor has script, which every few seconds during combat shows me his health, magicka, etc. I have level 4, actor's script shows level 4, mentioned stats as at level 1. When I get level 5, only actor's level is increased (= 5).
When I uncheck "PC Level Mult" and I set manually level = 4, actor's script shows me correct stats, which are calculated in Creation Kit.
But I want leveled summonable follower.