Mikrotik RouterOS view and set Simple Queue speeds

list all simple queues

queue simple print 

Print queue that matches part of name

queue simple print where name~"John"

Example results

Flags: X - disabled, I - invalid, D - dynamic 
0 name="John Smith" target= parent=none packet-marks="" priority=8/8 queue=sfq-up/sfq-down limit-at=0/0
max-limit=1M/10M burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s bucket-size=0.1/0.1 total-queue=default

Change max speed on queue for client name. The Upload is specified first.

queue simple set max-limit=10M/100M "John Smith"