As of v3.0.0, it is possible to automate using Tasker, Automate, Automagic or any automation apps that support Tasker plugins.

Open tasks in Tasker and go to Plugin. The textfields support Tasker variables, click on the blue icon at the side to access them.

1. Make sure the date field is in YYYY-MM-DD format.
2. Make sure the time field is in HH:MM format.(only 24 hour clock is supported)
3. Make sure the currency field is in three letter code. For example, Euro should be EUR.

Some sample tasks can be found here

The following broadcast receivers are supported too.

firefly.hisname.ADD_DEPOSIT
firefly.hisname.ADD_WITHDRAW
firefly.hisname.ADD_TRANSFER

Supported parameters:

description
source
destination
amount
category
budget
tags
time
date
piggybank

An example:

am broadcast -a firefly.hisname.ADD_WITHDRAW --es description 'An example withdrawal' --es date '2018-10-14' --es amount '1' --es currency 'usd' --es sourceName 'your_source_account' -n xyz.hisname.fireflyiii/.receiver.TransactionReceiver