In GNS3, by default, nothing will persist after reloading your project unless your Docker Container is configured to do so. Your Docker Container may not be configured to have persistent data. This behavior is described in the official GNS3 documentation.
By default nothing is persisted on disk. The container needs to be designed for that.
If in the Dockerfile the container mount volumes. GNS3 will create in the project folders a folder for each Docker volume and will write file inside.
This mean if you use a container outside GNS3 the data will not be available. But also this mean all the data of the GNS3 project is in the same location.
I guess your hosts are TinyCore Linux machines. TinyCore restores files -including startup scripts- from an archive and configures itself with those scripts. You should alter startup scripts and save it into the backup archive.
Edit /opt/bootlocal.sh and add your startup commands.
#!/bin/sh # put other system startup commands here ifconfig eth0 172.16.1.3 netmask 255.255.255.0
Rebuild backup archive using filetool script. It creates a backup archive including files and directories listed in /opt/.filetool.lst and excluding the ones in /opt/.xfiletool.lst (/opt is already included so you don't need to edit anything.)
Just in case
Restart the node
Now your node should be having a persistent configuration.