By multi level I mean two level of switches, router, switch one for passthrough tagging only, switch 2 for actual tagging ports. Tagging ports works if I plug it directly into router. Doesn't work as a second level after switch 1.
Unfortunately, the word "tagging" gets used to mean different things by different people, and what makes it especially confusing in this case is that the two uses are describing the exact opposites. When I use the word tagging, I try to limit that to the operation related to the IEEE 802.1Q tags that get "inserted" into the ethernet frames while they are "on the wire", and that's what I mean by a "tagged" vlan on a port. But even MikroTik uses the term tagging to describe what happens when an untagged ethernet frame (standard ethernet as is used by an out of the box PC) gets received on an access port, and the port vlan id (PVID; what SwOS uses the term "Default VLAN", what Cisco calls the "Native VLAN") is used to specify into which vlan the switch will "classify" the frame as belonging to. The point is I am not sure what you mean by your statement "switch 2 for actual tagging ports". It isn't clear to me if you mean switch 2 has access ports, or instead that switch 2 is applying tags on egress, as those are two very different things.
Now to your problem. Adding a switch in series should work, assuming it is configured correctly and is working hardware, and that the SFP modules are compatible with the switch firmware.
So my suggestion would be to make a backup of your CRS326Q (so you can restore later, when you know what needs to be fixed), then look at the examples in the documentation
, and configure two ports as identical trunk ports (or hybrid if one of the vlans on the link is untagged) and be sure the tagged and untagged vlans on those trunk ports agree with the settings on the devices they connect to. And I would recommend using strict mode like they do in the examples.
If you still can't get it to work with SwOS, would you consider using ROS instead of SwOS on the CRS326-24S+2Q+RM? At least that has a text mode config that you can export to upload to the forum.