Gifted Subs appear in the same tab as gifted Mixer Pro
Whenever you currently gift Mixer Pro to another viewer on Mixer, it appears on the billing section of your account on the 'Gifts Tab' here: https://mixer.com/browse/following(hub:me/billing/gifts)
At the minute there is no way to check who you have gifted a channel subscription to or who you have been gifted a channel subscription from unless you check invoices which are limited on how far you can go back or by digging through your e-mail inbox.
There has been a few times I've been lurking in channels and received a gifted sub and not known who gifted it after returning so was unable to thank them.
I was thinking it might be easiest to sort both Mixer Pro and Channel Subscriptions by "Gifts Sent" & "Gifts Received" on the one page. Basically Mixer Pro gifts wouldn't need to change much but would allow you to see who gifted you Mixer Pro in the past.
For Channel Subscriptions sent - you would see the 'order #' - who you gifted the subscription too and in which channel did you gift the subscription.
Channel Subscriptions received - you would see the username of the member who gifted you the subscription and in which channel.
It might take a while to get the right idea on how to display this information on the Billing>Gifts tab however I feel it will complete this tab as personally it's felt pretty empty unless you are someone who constantly gifts Mixer pro.