Hello wonderful people!
I have found a way to make a door in the middle of a map/room that you can walk through in both directions using simple eventing. This is for a locked door that requires a key. (To create a key just go into the database, add or edit an item ID slot, fill out the form however you like and then tick the box that says key item. Remember the number next to the item you just created!). I noticed that a lot of people where having issues with doors so I decided to post what I've found, I hope that it might be of use to someone!
So, here's how to do it:
Step 1) First off, create a door in events mode using the quick commands : (Short cut = Right click then press and hold Ctrl and click 2)

Step 2) Place/move it where you want the door and then edit the door : (Short cut = Right click then enter)

Step 3) Once in edit mode, input the following data (You can change the text to anything you want or remove it) : (Pay close attention to the graphic, priority and trigger)

Step 4) Then create a new page in the same event and input the following : (Pay close attention to the switch, graphic, priority and trigger)

Step 5) All done! Now you just need to test it! (see video below)
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Here is a video tutorial of this in action (Only 1min and 15 sec):
I hope this helped!
If it did please let me know :)