The user tutorial says
Navigate to Data > View All
Choose to filter by the model key
Hit Save Model
Input for path: /data/h2o-training/...
Hit Submit
The problem is that I do not have this menu (H2o, 3.0.0.26, web interface)
Answer
I am, unfortunately, not familiar with the web interface but I can offer a workaround involving H2O in R. The functions
h2o.saveModel(object, dir = "", name = "", filename = "", force = FALSE)
and
h2o.loadModel(path, conn = h2o.getConnection())
Should offer what you need. I will try to have a look at H2O Flow.
Update
I cannot find the possibility to explicitly save a model either. What you can do instead is save the 'Flow'. You ergo could upload/import your file, build the model and then save / load the status :-)