Sure! This is actually pretty easy to do. You'll gain the benefits of a full VRChat account, such as the ability to gain Trust Ranks and upload content, whilst keeping the simplicity of being able to log in with a single click when running VRChat via the corresponding platform.
Please log into VRChat with your Steam, Oculus or Viveport account. Open your quick menu, then select Settings. Near the bottom of that menu, you'll see a button to "Upgrade Account". Click that and follow the instructions on the screen to link your accounts.
Please note: If you have favorite avatars or worlds on the VRChat account that you are linking another account to, the merge will ignore the favorites on the Steam/Oculus/Viveport account. Think carefully about which account you want to keep your favorites from, and ensure your VRChat account does not have any favorites if you'd like to keep the favorites from the account you're linking it to. There is no way to recover favorites lost through this method.
It is possible for a single VRChat account to be linked to a Steam account, an Oculus account, and a Viveport account at the same time. As stated during the process, linking accounts is permanent and cannot be undone.
It can take up to a day for your account data to finish merging over. If you're having any issues with the process, please contact support at https://vrchat.zendesk.com/hc/requests/new.