[capink]

Here is a minimal "Convert Books" action based on calibre's auto-convert. It is non interactive, and follows the same settings as calibre's auto-convert.

from PyQt5.Qt import (Qt, QApplication, QWidget, QVBoxLayout, QHBoxLayout, QGridLayout,
                      QCheckBox, QIcon, QGroupBox)

from calibre import prints
from calibre.constants import DEBUG
from calibre.utils.date import now

from calibre_plugins.action_chains.actions.base import ChainAction
from calibre_plugins.action_chains.actions.calibre_actions import unfinished_job_ids, responsive_wait, responsive_wait_until

class ConfigWidget(QWidget):

    def __init__(self, plugin_action):
        QWidget.__init__(self)
        self.plugin_action = plugin_action
        self.gui = plugin_action.gui
        self.db = self.gui.current_db
        self._init_controls()

    def _init_controls(self):

        l = QVBoxLayout()
        self.setLayout(l)

        job_wait_chk = self.job_wait_chk = QCheckBox(_('Wait until all convert jobs finish.'))
        l.addWidget(job_wait_chk)
        job_wait_chk.setChecked(True)

        l.addStretch(1)

    def load_settings(self, settings):
        if settings:
            self.job_wait_chk.setChecked(settings['wait_jobs'])

    def save_settings(self):
        settings = {}
        settings['wait_jobs'] = self.job_wait_chk.isChecked()
        return settings

class ChainsConvertAction(ChainAction):

    name = 'Convert Books'
    support_scopes = True

    def run(self, gui, settings, chain):
        db = gui.current_db
        book_ids = chain.scope().get_book_ids()
        start_time = now()

        jobs_before_ids = unfinished_job_ids(gui)

        gui.iactions['Convert Books'].auto_convert_auto_add(book_ids)

        wait_jobs = settings.get('wait_jobs', True)

        if wait_jobs:            
            # wait for jobs spawned by action to kick in
            responsive_wait(1)
            
            # save ids of jobs started after running the action                    
            ids_jobs_by_action = unfinished_job_ids(gui).difference(jobs_before_ids)

            # wait for jobs to finish
            responsive_wait_until(lambda: ids_jobs_by_action.intersection(unfinished_job_ids(gui)) == set())         


    def config_widget(self):
        return ConfigWidget