In a GPS Exchange Format ("GPX") file, data is stored using the HTML concept of tagged elements:
Waypoint elements are enclosed between <wpt> and </wpt> tags
Route elements are enclosed between <rte> and </rte> tags
Track elements are enclosed between <trk> and </trk> tags
Each of these contains sub-elements, themselves enclosed in tags.

After importation (or manual creation), the sub-elements you are currently editing are now represented as columns within an SQLite database row (1 row per waypoint, route or track).

Element Visibility
'Settings' (accessible from the main screen) can be used to reduce screen 'clutter' during editing. Use these to show/hide:
(a) hdop and vdop
(b) Individual user0-user7 elements and associated spinners.
(c) user_i and user_r
(d) imgId and imgPath

What are Spinners?
Alongside type, symbol, id0, id1, user0-user7, Image path are drop-down value selectors.
These 'spinners' allow convenient selection of pre-defined values managed by an elaborate system of key-value pairs.
[key-value management is selected via the action bar 'face' icon. It allows for dynamic addition of new spinner values during the current editing selection. Spinner value sets may also be imported, exported, or merged with similar data gathered by fellow team members!]

For example, your policy is that user0 should hold tree names. To-day you are geo-tagging in your local forest and have encountered a chestnut for the first time. Instead of just typing "Chestnut" into the user0 field you create a new value "Chestnut" for key user0 then fill the actual user0 field from the updated spinner.

Using Spinners
Each spinner contains a set of values, one of which is the user-defined default value that appears alongside the associated field when editing commences.
1st objective is to make the value you want appears alongside the field.
You may:
(a) Do nothing (because you want to use your own default).
(b) Short press the spinner then choose from the full list.
(c) Start typing the actual value you want, then press the spinner and choose from a list that starts at the suggested value.
2nd objective is to get the spinner value into the field:
LONG PRESS the closed spinner to transfer the selected value!

Summary of editable elements
(showing relationship between database column and GPX element)
"*" denotes 'user-defined' element.
"+" denotes 'waypoint only'.

Name: Name of entity. <name>
Number: Number of entity. (signed integer).<number>
Desc: Description. Can be quite lengthy. <desc>
Comment: Comment, usually concise. <cmt>
Type: Category.<type>
Symbol: Symbol for point display. <sym>
Time: Timestamp. <time>
+Latitude: Latitude of point. [attribute 'lat=']
+Longitude: Longitude of point. [attribute 'lon=']
+Altitude: Elevation of point (metres).<ele>
+Hor. dop: Horizontal dilution of precision<hdop>
+Vert. dop: Vertical dilution of precision<hdop>
*id0: Primary classification for list filtering<id0>
*id1: Sub-classification for list filtering<id1>
*Image Id: Name of associated image file<imgid>
*Img Path: Path to associated image file ('binder')<imgpath>
*user0-user7: Anything you want <user0> - <user7>
*user_i: Anything you want (signed integer only) <user_i>
*user_r: Anything you want (signed decimal only) <user_r>

NB: Full Tables of Supported Elements are contained in the help offered after .gpx file analysis & import is selected from the main screen.

User-defined titles
In an above example the user0 field is used to hold tree names. To change the title from user0: to Tree: proceed as follows;
(a) Press 'face' icon in action bar;
(b) Filter for keys of 'alias'.
(c) Select the list item for 'alias user0 #title'
(d) Change target value to 'Tree:' then press 'Update...'
OR (if the required key-value record does not already exist)
(a) Press 'face' icon in action bar then press '+';
(b) Select key of 'alias' from the spinner
(c) Type 'user0' for the alias source value
(d) Type 'Tree:' for the alias target value
(e) Select '#title' from the binder spinner then long press it.
(f) Press 'Add new key-value'.
The new value will be applied to VIEW and EDIT operations for waypoints, routes and tracks after application restart.