Routing tables may exist even if no route is associated with them. e.g. a VRF with no assigned IP address on its interface. Or a mangle rule setting a routing mark.
But there must be an direct method, since they appear in the dropdown lists in winbox.
If not, this is the moment of a feature request
Torturing CCR1009-7G-1C-1S+, RB450G, RB750GL, RB951G-2HnD, RB960PGS, RB260GSP, OmniTIK 5HnD and NetMetal 922UAGS-5HPacD + R11e-5HnD in my home network.