Can new tasks be added to the bottom of the list?

Yes. You can achieve this with the following steps:

iOS / Android

1. Click Settings > General on the panel.
2. Click Task Default > Default Add to.
3. Choose Bottom of List.

macOS

1. Click the Avatar in the upper-left corner of your TickTick homepage  >   Settings from the menu that appears.
2. Click Task Default on the upper panel.
3. On the bottom of the page, you can see Default Add to, then choose Bottom of list.

Windows

1. Click the Avatar in the upper-left corner of your TickTick homepage > Settings from the menu that appears.
2. Click Features on the left panel, then click Task Default.
3. Scroll down the page till you see Default add to, then choose bottom of list.

Web

1. Click the Avatar in the upper-left corner of your TickTick homepage > Settings from the menu that appears.
2. Click Preferences on the left panel.
3. Scroll down the page to the bottom, then you can see Default Add to, then choose Bottom of List.