Manipulating the Goldsrc game menu items
The sizing and position of the menu items are directly influenced by the ProportionalBaseWidthHD or ProportionalBaseHeightHD parameters from 
resource/trackerscheme.res, even if hd_background is set to 0 in liblist.gam.
Item spacing
The spacing between items equals to MenuItemHeight * 1080 / ProportionalBaseHeightHD.
Left padding
In-game left padding equals to GameMenuInset x window height / ProportionalBaseHeightHD when window height > ProportionalBaseHeightHD. When window height <= ProportionalBaseHeightHD, then the GameMenuInset parameter seems to be an absolute value, in pixels.
I found an edge case in resolution 720x480 where the padding was scaled down despite what's written above. The logic was tested and worked on resolutions 1920x1080, 1680x1050, 1600x900, 1280x720 and 1176x664.
Bottom padding
Although apparently not set anywhere, bottom padding equals to 56 x 1080 / ProportionalBaseHeightHD
Font size
Font size is not proportional to resolution, but only to ProportionalBaseHeightHD.
Height of smallcap letters is MenuLarge.Tall * 11 / 28 * 1080 / ProportionalBaseHeightHD.