I'm interested if it's possible to add shortcut(icon) for webpage in Chrome's extensions sidebar. Or what it's called there, don't actually know, area next to address bar where other extensions icons reside.
I'm assuming you are talking about bookmarks and bookmarks bar. If that is the case, go to options (the three horizontal lines in the upper right-hand corner, just to the right of the address bar) then "Show Bookmarks Bar".
To add webpages to the bar, you can select the URL from the address bar and drag and drop it into the bar. You can also go to Options again, then to Bookmarks again, then select "Bookmark This Page", and lastly click "Done" when the message box appears. Both of these methods are assuming you are on the page you want to bookmark.
You can also select which bookmarks appear on the bar if you bookmark too many pages. To do this, go to "Bookmark Manager" under bookmarks. When the new window appears, place any bookmarks you want to appear on the bar in the "Bookmark Bar" folder.