KLOA is an outliner app. All screenshots in this page show Japanese UI, but of course you can use it in English.
KLOA works on Android 4 and above.
If you use Android 6 or above, you need to turn on the "Storage" permission in "Settings" of your phone -> "Apps" -> "KLOA" -> "Permissions", in order to save and load files.
When you launch KLOA at the first time, only one dot will show up. You can input text here.
If you enter a newline, the next item is created.
To change a level of an item, swipe the screen to left or to right.
To move an item up or down, drag up or down on the arrow button on the right side.
Tapping a dot at the top of an item expands/collapses children items.
You can undo and redo freely by buttons in the toolbar.
Long pressing on an item changes the toolbar, allowing you to cut, copy, and paste of an item. These action doesn't require selecting a range of text, because it automatically treat the current item and its children.
You can attatch a "note" text at an item. Pressing this button brings you to a note editor screen.
Write text as you like, and go back to the outline view. Note that if you press the "cross" button at the upper right, you can go back discarding changes.
To show notes permanently, turn on "Show notes" in the menu. Pressing the button on the left end also brings you to the note editor.
You can change size of the notes viewer by dragging the boundary.
In this app, documents can be saved where you want (such as a certaiin directory in the SD card). Functions in the "File" menu, such as "Open" and "Save as", work as in a ordinary word processor or a text editor.
Documents are saved in plain text files. You can open them by another app (for example, a text editor app) and see the format of the files. A text of an item is written in one line, preceded "*" mark. A level of the item is represented by number of "*" mark. (This mark can be set to any character in the preferences screen.) A note of the item starts from the next line of the corresponding item.
In reverse, a file in this format can be opened in KLOA, probably.
If you have a hardware keyboard, keyboard shortcuts may be available. By default, shortcuts are as following. You can change shortcut keys (a modifier key "Ctrl" also can be changed). Take a look in the Preference screen.
If you turn on "Use extra margin for IME" at the Preference screen, extra bottom margin at the bottom of the screen appears. This is to prevent the screen from moving up and down when the IME displays and hide something small(word corrections, suggestions, etc.).
You can set how big is the margin in pixels at the Preference screen. Use some try and error to decide the number.
Of course, when you are using a software keyboard, this setting is not so useful.