It has been asked by several users before (since
2016) and they answered that it will be implemented in the future. I've searched about it now in case there have been a new update, however, it is still not yet available. The most updated result I got is from twitter, posted last Feb 19, 2018 (
Click quote links to view the tweets on twitter) :
Is staking on the Coinomi wallet available now?
Sorry, not yet.