I want NOT WRITE rules in table at all. Removing after reboot - is write and then delete. I need some rules to set and work in memory till device will powered off. Like simple linux system can do in command line.
Mikrotik saves its configuration immediately with each change, so there's no way to keep a firewall rule from being saved in the configuration. Only safe mode makes changes "temporary," and those changes revert if your terminal session is disconnected before ending safe mode, and they commit when you end safe mode, so this isn't what you want.
I'm not really a fan of scripting things, but deleting rules at bootup with a script gives operationally the same thing as having lost them at power-off, so I don't see how that's "not a solution" unless you're wanting to have ANY commands be rolled back by a reboot, but you're only saying firewall rule here in your thread... (or are worried about someone dumping the flash memory and reading configurations while the router is powered off). Yes, it's a work-around, but it's a viable in most cases.
You could also use the partition feature to save a reference configuration if you just want something to fall back to - but it sounds like "anything that hits the flash memory is completely and utterly unacceptable" so I'm going to stop offering ways to achieve the stated goal because obviously there is a hidden agenda which makes the behavior more important than the goal.