Inverter can the connection be changed?

See if you can swap the inverter for a smaller one. Something around 100 - 150 W is plenty. You then could run it from a merit socket.

No need to swap the inverter you already have - a 400W inverter will only draw 35A when operating at full load. If only running at 100W, it will draw a similar current to a 100W inverter running at 100W - the load is more relevant than the maximum capacity of the inverter.

The first inverter I purchased (300W) had two sets of connectors - one for low power use (with a cig. plug), and another for higher power use (with alligator clips). Each was fused appropriately for the expected load.

If you're only running low power appliances, you'd be fine to run it through a merit plug, though given that the inverter has capacity for much more than a merit plug could handle, I'd put a 10-15A fuse in the wire so that if someone does try to run a bigger load from the inverter, the fuse will melt rather than the internals of the merit plug/socket.

For fusing I would check what the inverter comes with. Many of the quality inverters will do 2* peak for motor startup etc so may draw 50A for a short period if you wanted to run a small power tool.Check what the manufacturer recommends.

Enerdrive recommends for their 400 W inverter an 80AMP fuse.

http://enerdrive.com.au/wp-content/uploads/2016/02/Fuse-Cable-Sizing-Inverters-Inverter-Chargers.pdf

Also pushing the limits of a 40 AMP Andersen plug.

From an earlier thread on here:

The standard grey SB50 Anderson is rated around 120amps.Feb 14, 2017
Amps through the Anderson Plug - ExplorOz

https://www.exploroz.com/forum/134293/amps-through-the-anderson-plug

I assume the OP is using a SBS 50 Anderson plug:

From Anderson Power Products website - see page 53: SBS 50 product specs

https://www.connector-techals.com.au/media/wysiwyg/pdf/APP_Catalogue_Full.pdf

According to this document the connection are rated at 50 Amps and sorry.... but I cant see where it indicates 120 Amps but Ill happily be proven wrong :) I also cant find any reference to "Continuous uninterrupted rating is much higher".

It would be good to find that source of information for future reference.

Cheers

https://au.mouser.com/datasheet/2/22/DS-SB50-795422.pdf

UL rated for 120A while plugged together or 50A if "hot unplugged". But even those values are subject to qualification like ambient temperature, how dirty it is, etc, etc, etc