In the "Preferences" floater:
- "Audio & media" tab, "Media" sub-tab: check "Notify about streaming music changes"
- "Notifications" tab: un-check "Do not echo/log notify tips in chat"
Yes, in the "Inventory" floater, "File" menu, "Make new outfit" entry. Or in the "Appearance" floater, "Make outfit..." button.
If you just wish to add (or remove) an item to an outfit, it's however just a matter of adding (or removing) the said item from the inventory folder containing the outfit items ("outfits" are just inventory sub-folders with wearable items, objects and possibly gestures: there is no specific "outfit" location in v1 viewers: they can be anywhere in your inventory).
You may also use the "Inventory" floater "Worn" tab to easily locate your worn items. Nifty trick: fold and unfold the folder (by clicking on the small arrow, left of the folder name) containing your worn items in the "Worn" tab, then switch to the "Last open" tab of the floater: you will then see the whole outfit folder contents (worn or not). You may also open a second Inventory floater ("File" -> "New window") to easily copy/move items around from one folder to another (the two floaters will bear independent search filters, "Last open" tab, etc, unlike what happens in most other viewers).
Another thing you can do, is to organize the items of any given outfit in sub-folders (e.g. create a sub-folder for clothing items and move all such items in it, then another sub-folder for, say, BDSM items (cuffs, collar, etc), you could also make a sub-sub-folder in the clothing items sub-folder for the shoes, etc...); this allows to easily remove or add items via a right click on sub-folder (and "Take off items" or "Add to outfit"), for example, if you want your avatar to undress quickly...