Review Kaspersky Anti-Virus 2019 Review: Lightweight, Simple, Reliable

Although there may be no 'custom scan' option, per se, there is a 'selective scan' option, which allows anything the user wishes to be designated for scanning, be it individual files, folder, folders, or entire drives.....(which would certainly seem to fit the definition/spirit of a 'custom scan' in my book)
Extension for browser monitoring : KAV actually registers an extension for Chrome and for Firefox automatically, ; you have to enable it (since these browsers do not enable extensions installed from another app by default, nor do they allow themselves to be driven by another software) but they are here. The setup requires a couple clicks, that's not exactly difficult.