Your Steemit wallet is constant and the same everywhere either you are making use of desktop or mobile devices. There is no desktop wallet available for steem except for the steem wallet you are provided with whenever you log into your Steemit account.
This implies that you have to be security cautious with your Steemit account password to avoid loss of funds in your Steemit account. Ensure you back up your password (keys) safely for optimum security.
In conclusion, your steem wallet will always remain the same irrespective of the device you log in with either mobile or desktop. There is no special desktop for your steem wallet other than the one you are provided with.
Thanks for reading and I hope this helps.