TAB or the tabulator-key has two un-useful uses in RedAlert: First of all to close and reopen your sidebar (units and structure production, radar map), which can be useful while spec-ing a game and enjoy so greater overview - but then u don't have the stats, production and kill rates.
And secondly, to drive players, who start to practice Q mad mad mad as hell. Because of its location directly next to the Q-key and the 1-number-key for grouping-together, your chances are pretty high to accidentally press it. Then your sidebar vanishs, which will result in delay of new tank production and raging distress. This not only happens to so-called newbies, but as well to more experienced players, under stressful Q-situations. In normal RA-settings u cannot change that key, so solutions to deal with the issue are rare: Either u deal with it and focus on exact clicking, or u dismantle the button manually - therefore several youtube-guides already exist. Both options lack of ezziness and ad-hoc problem-solving. Therefore the Red Alert Guides proudly present the step-by-step way to deactivate that bitch of a hotkey:
1. Type in lobby-chat: /run redalert.ini
This order will open an alternative Hotkey-editor. U will find all named hotkeys (from the general settings) in mid of the data, with accorded numbers. Those numbers represent - in an international uniform manner - your keys.
Search for: KeySidebarUp and -Down, which let u scroll the sidebar by hotkey. But there is NO button for Sidebar in general.
2. Don´t be silly, make a safety copy-paste of the whole data!
Who knows, what will happen, or what miss-typing will occur. Safety first! Hehe...
3. ADD a new line: KeySidebarToggle
KeySidebarToggle is the name for the key, dealing with your sidebar. Usually it´s automatically your TAB key. To deactivate TAB, u need to re-order the hotkey by a customized number. So firstly, imagine a key u wanna address as new TAB.
<--- new line: + KeySidebarToggle=190
(note: =78 may differ, depends on your settings, but it´s unimportant for this case.)
4. Save new Key-Option:
To save these new settings, first close all RedAlert-Sides - except the redalert.ini-texteditor. Then save the .ini-file with the new Toggle - not "save under", just "save". Now u can reopen RA and reopen this editor like under 1. and see, if your change is saved correctly.
5. Test it in a skirmish-game.
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Two Comments:
Somebody may find this a cheat, but I ensure, that the whole adding-KeySidebarToggle is funkyfresh affirmed - he gave me this hint in first place. So a big thanks to U, Funky.
Other ones may find this as a Holy Grail of RA-Hotkeys, going down to its DNA andsososo. But it is not. Lol. Of course I tested numerous changes with my beloved testing-partner, like: Can u add a 5th bookmark with adding a line KeyBookmark5=. Does not work! The reason may be, that this .ini-file goes back to original-hotkey-settings, which had limited options.
To Allies:... -- By simply pressing backspace, U will see this on top left of your game-screen, where u now can give attacking orders and tactical stuff to only your allied teammates. 
To All:... -- With return button, U now have a same function key like F8 - but straight bellow your backspace key - to talk to all players in the game.
