You can zoom in and out with one hand by pressing the (...) menu button on Edge
the magnifying glass icon appears on the address bar (Omnibox) when the zoom level of the web page you are visiting is different than the default zoom level, which can be set here: edge://settings/appearance
so based on that info, you can change your default zoom level to something other than 100% and then the magnifying glass icon will always be shown in the address bar when zoom level is not 100%.
if you want extensions, there is one here:
Zoom it - Microsoft Edge Addons
the rest of the extensions related to zooming: Microsoft Edge Add-ons - zoom