Have added two new features and amended proximity alarms in latest release.
Join TracklogsYou can now join tracklogs together by simply selecting multiple GPX files containing tracklogs. It does the rest by looking at the start timestamps of each tracklog segment, and sequencing them in chronological order. Tracklog segments are kept intact and a single GPX tracklog is returned in a zipped file. The GPX and zip files are named according to the earliest timestamp found. None of the simplification steps are applied during this operation. You'd need to load up the resulting single tracklog in a second step to apply simplification to it, to reduce its size etc, if an online service objects to overly large tracklog files.
Something I'll be using myself on my 400km audax next month, where I normally auto split tracklogs at midnight, and rejoin them after the event.
Distance Based Waypoint AlarmsYou can now add distance based waypoints with proximity alarms for supplied tracks. The waypoints occur at your specified distance interval, with the prefix you choose, with a suffix that indicates the distance the waypoint occurs at. I give them the red pin 📍 symbol which is recognised by Garmin software but may not be recognised by other software.
Proximity Alarm RadiusYou can now set the proximity alarm radius (for existing waypoints) to 25m after a request for that option.
Under The CoversI've now changed it to run in a Docker container as Heroku's version of NodeJS was getting long in the tooth. Now runs on Alpine Linux 3.15.1 and NodeJS 17. Also more easily moved should I need to move away from Heroku.