I'd like to suggest a following feature with vMix input list thumbnail for titles:

Lower thirds or other dynamic title inputs can appear the text unreadably small in the input list.
In order to avoid picking the input to preview to view it larger, title inputs could have an user option to automatically zoom the title to fill input thumbnail.

An example of the concept is included in the attachment.

title zoom example.png (20kb) downloaded 0 time(s).

Likely steps for implementation:
1) estimate the bounding box of title input content
2) determine the appropriate (minimum) translation for the bounding box to fill the input size
3) apply the transformation to the input list thumbnail