As of 5.61 the preview button in the store shows the wrong interface for me. Pressing escape does nothing and pressing the back button sometimes breaks the menu further by drawing it in the opposite order (HUD and controls only work while the menu is showing).
Here is my custom.cfg:
nick "uke"
mousebuttons "1"
backgroundclick "0"
volume "13"
musicvolume "0"
voicechatvolume "45"
fullscreen "1"
autosave_rpl "1"
rememberrules "0"
framerate "60"
shaders "1"
fluid "1"
reflection "1"
softshadow "1"
ambientocclusion "1"
bumpmapping "1"
raytracing "1"
noreload "1"
width "2560"
height "1440"
beginner "0"
newmenu "1"
languagesteam "0"
language "data/language/english.txt"
chattoggle "96"
chatfocus "0"
voicechattoggle "113"
particles "0"
trails "1"
hair "1"
hairquality "0"
obj "1"
bodytextures "1"
fixedframerate "1"
replaycache "1"
chatcache "1"
filesort "2"
worldshader "1"
effects "2"
matchmakerx "0"
matchmakery "100"
matchmakerhidden "0"
clanuipopup "0"
memsize "1"
highdpi "1"
keyboardlayout "0"
customworldshader "data/shader/default.inc"
autoupdate "1"
personal "1"
tooltip "0"
movememory "1"
chatcensor "0"
objshadow "1"
showbroadcast "1"
uilight "0"
menudebug "0"
jointflash "1"
shout "1"
shout_default "1"
dismember "1"
dismember_default "1"
fight_alert "1"
fight_alert_default "1"
freeze "1"
freeze_default "1"
game_over "1"
game_over_default "1"
grading "1"
grading_default "1"
grip "1"
grip_default "1"
hit "1"
hit_default "1"
impact "1"
impact_default "1"
joint "1"
joint_default "1"
menu "1"
menu_default "1"
none "1"
none_default "1"
pain "1"
pain_default "1"
ready "1"
ready_default "1"
select_player "1"
select_player_default "1"
splash "1"
splash_default "1"
swoosh "1"
swoosh_default "1"
blood "2"
grnewgame "1"
replayhudtoggle "9"
borderless "0"
playertext "1"
dpiawareness "0"
itemeffects "1"
usagestats "1"
shopnews "0"
guidpi "16"
jointobjopacity "100"
systemcursor "0"
bloodstains "1"
invertedcam "0"
camerafocus "1"
mipmaplevels "1"
tooltipmode "0"
camerasensitivity "100"